Two types of polarization of antenna are frequently used, linear polarization (LP) and circular polarization (CP). When wave of CP is used for satellite communication, it is less sensitive through ionosphere than the LP wave in terms of polarization; hence it is applied in satellite and other wireless systems like GPS to become the design trend of the recent research, development and application.
DRA is usually operated in a TE111 mode, and the mode has a wide beam linearly-polarized radiation pattern with a bandwidth of approximately 5-8% and having advantages of low loss and high radiation efficiency. In a common circularly-polarized DRA, an oblique aperture can be used to excite two modes with mutually orthogonal electric fields, to radiate circularly-polarized wave. Alternatively, a metal sheet is adhered to the surface of the dielectric resonator of the antenna, to perturb its original electric field distribution to generate two mutually orthogonal electric fields and generate the circular polarization. Alternatively, an annular or U-shaped aperture is used to excite the circularly-polarized electromagnetic wave from the dielectric resonator, but the bandwidth having an axial ratio (AR) smaller than 3 dB is approximately 3%, which has a much smaller bandwidth as compared with a common linearly-polarized DRA which can reach 5-8% of bandwidth. The linearly-polarized bandwidth of the DRA is mainly affected by the dielectric constant of the antenna and the shape thereof, and generally, if a material with lower dielectric constant (e.g., ∈γ□10) is used, the bandwidth can be improved by about 10%.
U.S. Pat. No. 6,147,647 B1 published on Nov. 14, 2000, titled “Circularly polarized dielectric resonator antenna” disclosed a dual-band dielectric resonator antenna, comprising: a first resonator formed of a dielectric material; a first ground plane formed of a conductive material on which said first resonator is mounted; a second resonator formed of a dielectric material; a second ground plane formed of a conductive material on which said second resonator is mounted, said first and second ground planes being separated from each other by a predetermined distance; and first and second probes electrically coupled to each of said resonators spaced approximately 90 degrees apart around the perimeter of each resonator providing first and second signals, respectively, to each resonator, wherein each of said resonators resonates in a predetermined frequency band that differs between said resonators
Additionally, U.S. Pat. No. 6,995,713 B1 published on Feb. 7, 2006, titled “Dielectric resonator wideband antenna” disclosed a wideband antenna consisting of a dielectric resonator or DRA mounted on a substrate with a ground plane. The resonator is positioned at a distance x from at least one of the edges of the ground plane, x being chosen such that 0.1 toreq.x.ltoreq . . . Lamda . . . sub. die ½, with .lamda . . . sub. die ½ the wavelength is defined in the dielectric resonator.
Also, U.S. Pat. No. 7,196,663 B1 published on Mar. 27, 2007, titled “Dielectric resonator type antennas” disclosed a dielectric resonator antenna comprising a block of dielectric resonator having a first face intended to be mounted on ground plane and entirely covered with a first metallic layer, wherein at least one second face perpendicular to the first face is covered with a second metallic layer contacting said metallic layer covering said first face, said second metallic layer covering said second face extending over a width less than the width of the second face and over a height less than or equal to the height of the second face, and wherein said block of dielectric resonator comprises a third face being at least partially unbounded by conductive material so as to emit radiation from said third face.
However, above-mentioned DRAs, for example U.S. Pat. No. 6,147,647 “Circularly polarized dielectric resonator”, U.S. Pat. No. 6,995,713 “Dielectric resonator wideband antenna”, and U.S. Pat. No. 7,196,663 “Dielectric resonator type antennas”, all related to a rectangle DRA, huge affect will be brought to the wireless communication field, whenever the circular polarization and the bandwidth can not be improved at the same time.